Online advertising has become a significant aspect of the web browsing experience. A number of advertising delivery systems currently operate to select and deliver contextual advertisements for placement on, for instance, web pages and search result pages. In the context of web pages, advertising delivery systems operate to analyze the text of the web pages to identify keywords that are used for selecting advertisements for placement on the web pages. In the context of search, when a user submits a search query to a search engine, keywords are identified based on the terms of the search query and/or based on content of the search results. The keywords are used for selecting advertisements that are presented in conjunction with general search results for the user's query.
Typically, advertising delivery system providers receive payment from advertisers based upon pay-per-performance models (e.g., cost-per-click or cost-per-action models). In such models, the advertisements returned with search results for a given search query include links to landing pages that contain the advertisers' content. A search engine provider receives payment from an advertiser when a user clicks on the advertiser's advertisement to access the landing page and/or otherwise performs some action after accessing the landing page (e.g., purchases the advertiser's product).
In the pay-per-performance model, advertising delivery systems select advertisements for web pages and search queries based on monetization. In other words, advertisements are selected to maximize advertising revenue. This is often performed through an auction process. Advertisers bid for particular words and/or phrases as a way for selecting advertisements and determining the order in which advertisements will be displayed for a given web page or search query. Bids are typically made as cost-per-click commitments. That is, the advertiser bids a dollar amount it is willing to pay each time a user selects or clicks on a displayed advertisement selected and presented as part of a web page or a result of a given search query.
In some instances, analysis of some web pages and search queries may only identify keywords that have not been bid on by advertisers or may result in only minimal keywords that have been bid on by advertisers. As a result, only minimal or no advertisements are selected for presentation on these web pages or in conjunction with search results for these search queries.